Since Brockett[1]} introduced the idea of translation to solve the problem of GEC by translating error text into right one, a lot of sequence to sequence models have been applied to GEC [2]}, [3]}, [4]}, [5]}. All of these studies are based on two public corpora, the largest parallel corpus Lang-8 [6]} and NUS Corpus of Learner English (NUCLE) [7]}.
